Born into a prominent family in the Electorate of Hanover, and married into another, in 1740 she became a naturalised subject of Great Britain and was granted a peerage for life, with the title of "Countess of Yarmouth", becoming the last royal mistress to be so honoured.

She remained in England until the death in 1760 of King George II, who is believed to have fathered her second son, Johann Ludwig, Reichsgraf von Wallmoden-Gimborn.

[3] In 1736, she bore a son, called Johann Ludwig Graf von Wallmoden-Gimborn, said to be the unacknowledged illegitimate child of the king.

In 1739, Johnson wrote scathingly of the king's relationship with Wallmoden, "his tortured sons shall die before his face / While he lies melting in a lewd embrace".

[2] Robert Walpole indicated that her primary focus was on pleasing the king, although she was also said to be interested in the bestowing of peerages, reputedly playing a part in the creation of a Barony for Stephen Fox-Strangways in 1741 and in the newly created title of Viscount Folkestone for Jacob des Bouverie in 1747.